Dispenser heads are known in which the dispenser orifice is permanently open.
Such dispenser heads are not suitable for dispensing a substance that is liable to form a solid residue on drying out.
Proposals have therefore been made for dispenser heads in which the dispenser orifice is closed except during periods of use, so as to prevent the substance from drying out inside it.
In particular, U.S. Pat. No. 3,250,474 discloses a dispenser head having a nozzle that is capable of being displaced relative to the body of the dispenser head. The body has a pin arranged to engage in the dispenser orifice during periods of non-use.
Such a dispenser head is relatively complex to make.
In addition, for reasons of mechanical strength, the diameter of the pin must not be made too small, so the dispenser orifice needs to have a diameter that is relatively large, thereby preventing the substance being dispensed at a low flow rate.